Field of the Invention
The present invention relates generally to a power tool that may be a drib press, and more particularly to belt tensioner for use in a drill press.
Description of the Related Art
Drill presses are commonly available tools in both commercial and home workshops. A common configuration of a drill press, also known as a pedestal drill, pillar drill, or bench drill, includes a stand that supports a work table, above which is a drill head. The stand may be configured for support on the floor or on a bench or other surface. The drill head includes a number of handles, or a wheel, that is operable to control the vertical movement of a spindle and chuck for holding a drill bit or other tool. A motor in the drill head drives the spindle and chuck. The drill bit or other tool in the chuck may be lowered toward a work piece on the work table by user manipulation of the handles or wheel as the chuck and spindle are driven so that the work piece is drilled or otherwise shaped or formed. User manipulation of the handles or wheel in a reverse direction raises the drill bit from the work piece.
A drill press may be used to drill holes or form materials using the tool held in the chuck. The drill press may have a more powerful motor than a hand-held drill to facilitate drilling and forming of harder materials or to provide faster working of the material. The drill press may be used to control the accuracy of drilling or forming by controlling the drilling location, angle of the bore, and even the depth of the bore more readily than a hand drill. Larger bits may be used without strain on the user's hand and wrist. Less effort is needed to operate the drill press compared to a hand drill. The drill press may drill holes more accurately and more consistently compared to a hand drill, with a more powerful motor.
Drill presses may be operated at different speeds. One way of providing differing speed operation of the drill press is by use of a belt that is selectively movable to different positions on a stepped pulley arrangement that transfers rotational energy from the motor to the spindle. In belt driven drill presses, the belt must be capable of being moved from step to step in the stepped pulley arrangement. After adjustment of the belt position, it must be possible to apply tension to the belt to avoid slipping of the belt on the pulleys.
A known drill press (shown in U.S. Pre-Grant Publication 2011/0306451) includes an idler roller that presses on the belt to provide tension to the belt during operation of the drill press. The idler roller may be adjusted between two settings and includes a spring acting on the roller to provide tension on the belt.
It is possible for the belt to slip during use of the drill press, as a result of which the drill press does not use all of the power of the motor. Power is lost in the transfer of energy from the motor to the spindle. It is possible to stall a drill bit in a work piece during use of the drill press. If some of the motor power is lost in the transfer, the drill bit will stall at a lower power if the belt connecting the pulleys slips on one or both pulleys. On the other hand, if all of the motor's power is being transferred to the drill bit, the drill press will not stall until the motor stalls, which provides greater power to the drill bit if the belt is not slipping.